Apparatus for fusing powdered materials



y 1935- P. P. ALEXANDER 2,003,167

Inventor Peter F. Alexander,

H is Attorn ey.

UNITED STATES PATENT OFFICE;

FOB

APPARATUS MAT FUSING POWDEBED ERIALS Peter P. Alexander, Marblehead, Mass... assiguor to General Electric Company, a corporation of New York Application January'il,

3 Claims.

The present invention relates to a method and apparatus for fusing powdered materials to a relatively soft foundation metal such as steel or iron. In my copending application Serial No. 5 411,634, filed December 4, 1929, now Patent No. 1,971,804 I have disclosed an apparatus and method for spraying a powdered hard metal composition, for example a mixture of tungstenoarbide and cobalt heated to an elevated temperature, on to steel. In my prior process the powdered materials are heated by radiation from a carbon heater. However, in certain applications it is necessary to provide a coated article in a short period of time. Under such circumstances the heat radiated by the heater of the prior disclosure may not be sufiiciently intense to accomplish the desired result.

, To obtain heat necessary to fuse or glaze a hard metal composition in a short period of time, I employ a gas torch of the type disclosed in the copending application of Boris V. Nagashev, Serial No. 477,508, filed August 25, 1930, now Patent No. 1,911,033. A torch of this character produces a long narrow jet of gas sufficiently superheated to melt the cobalt constituent of a hard metal composition such as tungsten carbide and cobalt, in a very short period of time.

-The novel features which are characteristic of the present invention are set forth with particularity in the appended claims. The invention itself however will best be understood from reference to the following specification when considered in connection with the accompanying drawing in which the single figure is a view partly 35 in elevation and partly in section of an apparatus whereby my invention may be carried into effect. Referringmore particularly to the drawing, 1 have indicated at I, a metal or other suitable framework, on which the apparatus employed in carrying out my invention may be mounted. A gas are torch 2 is mounted adjacent the base of the framework I. The torch ordinarily comprises three adjustable tungsten electrodes, two of which, I and l, are indicated on the drawing; The electrodes are connected to a source of alternating current supply through a cable 5. A capillary or small bore conduit or tube 6 having an outside diameter of about of an inch and an inside diameter of about 20 mils is centrally disposed with respect to the torch electrodes. Tube is enlarged slightly at point 1.

and mounted with the electrodes in an electricallyinsulatingcasingl. Anasbestosshieldl ispositionedonthecasingladiaeentthelower end thereof and is secured tberetoby a suitable '1931, Serial No. 507,709

refractory cement Ill. An elongated conduit ll, similar to conduit 6 and in alignment therewith, is connected to the upper end of the enlargement 1.

The flow of gas issuing from the nozzle of the torch 2 consists of two distinct streams. The inner one issues from the tube 6 and consists of a. narrow high velocity gas stream l2 which passes through the arc. This stream comprises super;- heated gas which transmits the necessary energy 10 from the arc to the glazed or fused surface. In the present apparatus the narrow stream of gas carries the particles of powdered materials which are to be fused or glazed to a foundation metal. To obtain the high velocity, narrow jet of gas, a

' pipe I3 is connected through a valve I4 to a gas supply pipe l5. Pipe I3 is connected to the tube II at the upper end thereof. A mercury gage It indicates the gas pressure in thepipe l3.

The second jet of gas issuing from the torch 2o nozzle is a low velocity jet I! which completely surrounds the high velocity jet [2 and the piece to be glazed. The purpose of the low velocity jet is. to provide a shielding atmosphere for the torch electrodes, the central high velocity gas jet and the surface to be glazed. The gas for the low velocity jet is supplied through a pipe l8 which is connected at one end thereof to the gas supply pipe l5 through a valve IS. The other end of the pipe I8 is connected to the inside of the torch nozzle so that .the low velocity gas completely fills the space inside the torch nozzle and around the torch electrodes.

A receptacle 20, adapted to contain the powdered materials to be deposited and fused or glazed to a foundation metal is mounted on the framework l and at the upper end of tube ll. Receptacle 20. is similar in construction to an ordinary sight feed oil cup. A screw 2|, mounted in the upper end of the receptacle, controls 40 the usual feed valve in the receptacle and thereby regulates the feed of powdered materials to the tubes II and 6. This feed valve of course can be of any other design which accomplishes the same purpose, that is, the fine regulation of the amount of powdered material supplied to the tubes H and 6.

An electrically operated vibrator 22 is positioned on the framework I and connected to the upper end of the tube II to vibrate the latter and thereby prevent the powdered material from adhering to and becoming packed in the tube.

A pipe 13 connects receptacle 2| with a second mercury me 24 which indicates gas pressure above the powdered materials in receptacle II. 5

Pipe 23 is connected to pipe l3 through a valve 25 ,so that a desired gas pressure may be maintained above the powdered materials in receptacle 20.

An open ended pipe 26 having a valve 21 mounted therein is connected to pipe 23. Before starting operations it is sometimes desirable to blow out the receptacle and the gas pipe 23. This may be accomplished by opening valves 27 and for a short time.

In operation, receptacle 20 is filled with powdered materials, for example a mixture consisting of about 87 parts tungsten carbide and 13 parts cobalt. A steel block or other material 28 tobe surfaced with the material in receptacle 20- is positioned on fire bricks 29 mounted at the lower end of the framework l and the gas are torch 2 placed a suitable distance above the steel block 28. The torch electrodes are then adjusted so that their terminals approach within arcing distance of one another. Vibrator 22 is set in motion and valves l4 and I9 opened to supply hydrogen gas to the torch. An arc is then struck between the torch electrodes. Screw one-half to 65-lbs. per square inch, according to the size ofthe jet and the current in the arc and has suiiicient velocity to draw the superheated gases into a narrow, long intense jet.

The powdered material fed through pipe H- and emerging from tube 6 is not melted before it reaches the steel block 28- but is deposited in a powdered condition and then fused thereon.

on the steel base 28 nor does it crack whenheat treated or when severely quenched. The fused deposit may be forged and its homogeneity thereby materially improved. Forging moreover substantially eliminates any voids which may be present in thedeposited material.

I have forged a layer of fused material initially consisting of about 13% cobalt and 87% tungsten carbide at a temperatureof 950 to 1000 C. At this and higher temperatures the deposited material was relatively soft and the original thickness of the layer was reduced considerably by the forging operation. After forging, thefused layer and supporting 'steel structure were quenched, while still at a temperature of about 300 (3., in cold running water. The quenching j operation was given for the purpose of imparting suficient hardness to the high carbon steel base as on which the powdered materials were deposited and fused thereto. The layer of fused material did not crack either during the forging or subsequent quenching;

While I have illustrated my invention in connection with only one powdered composition, it is obvious that the invention is notlimlted to that particular composition but may be employed equally well in glazing and fusing other powdered compositions. Any change in composition of course imparts different properties to the deposited material. For instance, with higher percentages of refractory carbides the deposits are much harder and less ductile.

Although I find it desirable to feed the powdered material through a capillary or'small bore tube 6, it is not absolutely necessary to do so. The powdered material may, if desired, be placed on the material to be coated and the torch then applied to the powdered material to fuse it to the foundation metal.

Although I prefer to employ a gas-arc torch such as disclosed on the drawing, the invention is not limited to the particular features of construction disclosed. Other forms of torches may be employed if desired provided they supply a non-oxidizing atmosphere and develop the high temperatures necessary for this work.

While I prefer to employ hydrogen gas and tungsten electrodes in the torch, the process has been carried out with carbon electrodes and with various gaseous mixtures which are non-oxidizing and non-decarbonizing for example hydrogen with propane, carbon monoxide, hydrogen with nitrogen, and even with substantially pure nitrogen. The monatomic gases such as argon and helium may alsobeused in this process. If a gas, such as hydrogen, which can be dissociated into its atomic state, is employed, an atomic flame may be formed in which the heat lsderived from the recombination of the atoms to form. molecules.

The deposition and glazing of the powdered materials onto the foundation metal 28. may be carried out continuously or intermittently. If a large surface is to be coated, it is desirable to continuously glaze the surface. However, for glazing small pieces of metal such as the edges of cutting tools, it is preferable in the interests of accuracy and economy to deposit the metalintermittently on the tool edge. The metal 28 may be moved in a horizontal direction under the gas torch in order that any portion of the surface of the metal may be coated. .The foundation metal may also be adjusted in a vertical direction.

It, is sometimes desirable to preheat the foundation metal. Under such circumstances, I connect one phase of the three-phase system indicated .at 5 to the metal 28 and the other two phases which forms a smooth and sometimes shiny-sur- This thin layer is not transparent since face. it consists of an opaque material. Under certain conditions, when the powdered material is desegregates into a large drop on the surface of the foundation metal and spreads'over the foundation metallike warm oil'over the surface of posited intermittently, it is first melted. It then a piece of ice. If the application of heat is A Letters Patent of .the United States, is:

1. In combination, a gas are torch comprising a casing, a plurality oi electrodes adjustably positioned relative to one another in said casing, a conduit positioned in said casing to direct a blast of gas between the arcing terminals of said electrodes, means for supplying gas and a powdered composition to said conduit, and means for vibrating said conduit.

2..In'combination, a gas are torch comprising a casing, a plurality of electrodes adjustably positioned to one another in said casing, a capillary conduit positioned in said casing and arranged to direct a blast .of gas between the arcin; terminals of said electrodes to thereby produce a narrow superheated jet of gas, means for supplying powdered material and gas to said conduit, means for vibrating said conduit, and

means for supplying gas to the nozzle of the I torch to provide a shielding atmosphere for said electrodes and said narrow jet.

3. In combination, a gas are torch compris ing a casing, a plurality of electrodes adjustably positioned relative to one another in said casing, a conduit positioned in said casing to direct a blast of gas between the arcing terminals 01' said electrodes to thereby produce a long narrow gas jet, means whereby a shielding atmosphere may surround said jet, and means7ior supplying powdered material to said jet. 1

. PETER P. ALEXANDER. 

